Nonsticky water and flame resistant insulated conductor, conduit, etc., and method of making



Jan 931; .J. A. KENNEDY 1,737,629

NONSTICKY WATER AND FLAME RESISTANT INSULATED CONDUCTOR,

CONDUIT, ETC. AND METHOD OF MAKING Filed Oct. 2. 1928 Patented Jan. 1931UNITED STATES PATENT OFFICE JOSEPH A. KENNEDY, 0] PAWTUCKET,RHODE'ISLAND, ASSIGNOB, BY MESNE ASSIGN- IENTS, T0 ANACONDA WAREnonsrrcxx warm m m AND CABLE COMPANY, A CORPORATION 01' DELA- IILAIERESISTANT INSULATEl) CONDUCTOR, CONDUI'I, E'I'C.,

AND METHOD 0! MAKING Application fled October 2, 1928. Serial No.309,502.

' This invention relates to the art of waterresistant and flame-proofedinsulated electrical cable and other conductors, non-metallic flexibleconduit for receiving and protecting electrical conductors, and othermanufa'ctures of similar character. It is concerned with methods oftreating such manufactures to make them not only water-proof andflameproof within the limits of established practice, but alsonon-sticky on the surface.

' Such goods are treated with compounds to render them water-proof andflame-proof, conforming to the standards established by the NationalBoard of Fire Underwriters. Heretofore asphaltum has been commonly usedas the water-proofing compound, and stearin itch as the flame-proofingcompound, the asp alt being first applied and caused to penetrate andimpregnate to a greater or less extent the sheathing of the conductorcable or the structure of the conduit, and the stearin pitch beingsubsequently applied as an outer coating. While these substances aresatisfactory from the point of view of the underwriters requirements andcost considerations, the stearin pitch coating has the objectionablequality of being sticky. It is a semi-solid amorphous substance whencold,

and is liquefiable by heat. It is applied to the goods by passing thelatter through a body of the stearin pitch contained in liquid conditionin a heated tank. After heating and application in this manner, itssticky condition persists even after cooling, so that when the coatedgoods have been rolled into a coil for storage and shipment, the ,turnsof the coil adhere together and the coating is liable to be more or lessstripped oif when uncoiled; and also the sticky material soils the handsof users and anything else with.

which it may come in contact. In the efiort to overcome this stickyquality, the practice has been commonly followed of passing the coatedgoods, after leaving the tank of melted stearin pitch, through a loosemass of mica flakes or powdered talc, some of which will adhere more orless firmly tokthe sticky coat= ing. But the protection given'by thismeans is not complete andsatisfa'ctory. Another efiort in the samedirection, which consists in'applying an additional coat of paraflin orother wa substance over the stearin pitch has met with greater success.Both of these treatments, however, involve material, and a step in theprocess, additional to the commonly used asphaltum and stearin pitch,and to the processes followed in applying these substances.

Accordin to the present invention, I obtain the desired effect ofwater-proofing and flame-proofing the goods, and overcoming thestickiness of the flame-proofing coat, by successive treatments with waxand stearin pitch, eliminating the use of asphaltum altogether and thestep of applying powdered mineral or melted wax on the surface oftheflameproofing compound. In this new treatment the wax impregnation takesthe place of asphalt impregnation and obtains an equally.

successful water-proofingefl'ect. It likewise neutralizes or overcomesthe surface stickiness of the stearin pitch coat. The last named effectis due to the fact, which I have discovered and utilized industriallyfor the first time, I believe, that when wax of lower meltadhesivequality of the external surface of the stearin itch coating and producea waxy feeling to t e touch, but is insufiicient to increase theinfiammability of the stearin pitch coat appreciably. It does not existon the slfirface of the pitch coating as a distinct film o wax.

The steps of the process and characteris:

tics of theproduct in which this invention resides are more fullydescribed in the following specification, in connection with thedrawings. In the latter,-

I Figs. 1, 2 and 3 are diagrammatic views illustrating the nature of thesteps performed in impregnating a cable or electrical conduc-'torsaccording to this invention but without attempting-to show thedetails of the commercial apparatusen ployed; v p

Fig. 4 is a fragmentary elevation of a partially dismembered cableembodying this invention;

Fig. 5 is a fragmetary partial elevation and partial section of aconduit for electrical purposes embodying the same invention.

The invention may be applied to the treatment of all types of flexibleinsulated electrical conductors or cables, and flexible nonmetallicconduit designed to receive electrical conductors and for like uses. InFig. 4 I have shown illustratively a cable consisting of two insulatedwiresaand bwhich are Wrapped about with strands of twisted paper orother equivalent cords in order to preserve and maintain a prescribeddistance between the metallic cores of the individual conductors, andare laid side by side, in conjunction with thick filler cords (Z, (Z,into a cable which is covered by a sheath 6 constructed of interwoven orbraided strands. In Fig. 5 I have shown a flexible non-metallic conduitof the typp shown in the Smith Patent No. 1,016,527, Fe ruary 6, 1912,as illustrative of another class of goods in which the invention may beembodied, such conduit being constructed of lon itudinal warp strandsand helical weft or lling strands.

In applying the treatment of this invention to a cable, the separatewires, with their surrounding strands 0, are passed through a tank Itcontaining a body of melted waxand heated .by gas flames 2' or otherwiseto a temperature high enough to keep the wax in melted condition. Afterthe wax thus applied has be-.

come solid, the wires are combined in a cable and covered with the wovenor braided sheath 6. The entire cable is then passed through a similarheated tank j containing wax in melted condition; The wax issufficiently fluid and the cable is passed through the tank slowlyenough to permit a substantiall complete impregnation of the sheath andthe component "strands thereof by thewax. As the cable emerges from thetank the surplus wax adhering to its surface is wiped off by means wellunderstood in the art.

In these treatments I may use any wax which has a melting point lowerthan that of stearin pitch and is sufiiciently thin when melted topenetrate into and between the strands of the sheath, as above setforth. Paraffin wax is suitable for this purpose and may serve as anillustration of a large class of equivalent waxes having the desiredproperties.

The procedure above described, so far as concerns the preliminarytreatment of the wires before being covered with the sheath 0, may bemodified or omitted "without departure from the invention. Thus, in thecase of cables containing two or more wires differently colored todesignate different polarity, the light colored wire or wires may betreated with a clear wax, and black or other; dark colored wires treatedwith a different suitable compound, if desired, to reduce expense or forother reasons. Or indeed the preliminary wax treating ma be omittedaltogether and the treatment a ter application of the sheath relied onto permeate the covering strands 0, and 'even the braided jackets of theindividual Wires.

Finally the wax impregnated cable, after cooling, is passed through atank In containing a body of melted stearin pitch maintained in asufliciently fluid condition, by-the heat of gas flames under the tankor othersuitable means, to permit immersion and passage of the cablethrough it, In leaving the tank the cable passes through a die or wiperwhich removes the excess of stearin pitch. A second coat of stearinpitchmay be applied if desired by a repetition of the step lastdescribed.

The heat of the stearin pitch bath melts the previously applied Wax; andthe free melted wax, that is, so much of it as-is not retained in thesheath by capillarity, percolates through the enveloping coat or coatsof stearin pitch and appearson the surface of the outer coat insuflicient quantity to give it a slightly waxy feeling to the touch andmake it completely nonadhesive either to adjacent bodies of the samematerial, to the hands of the user, or to other objects with which itmay come in contact. But the wax does not make a perceptible film on thesurface, neither is it present in suflicient quantity to burn whensubjeced to the flame test, or to impair the ability of the stearinpitch coating to conform to the established flame-proofing standards. Itleaves the sheath highly flexible and avoids deposit of a black stickycompound on the inside of the sheath and on the individual wires. As theresult of using wax in this connection the stearin pitch coating doesnot y penetrate through the meshes of the sheath goods are treated byimpregnation first in melted asphaltum and then in melted stearin pitch,the black compounds usually penetrate the sheath more or less, leaving asticky deposit on the inside of the sheath which soils the hands of theworkman when removing the sheath preparatory to connecting up the wires,

and also discoloring those wires which aregiven a light colorforpolarity distinction.

Conduits are treated according to this invention in the same way asabove described with respect to cable. Indeed an 0 en conduit of wovenconstruction is essentially the same as the outer sheath of a cable orother insulated conductor, so far as the invention is concerned. Itdiffers in having an :open interior instead of being filled with wires,etc, but it is so passed through the baths of wax and stearin pitch thatthese materials are applied to it on the outside only and penetrate onlyto the extent that they can soak into the interstices during the timethat a given point in the length of the conduit remains in the bath. Thesame qualities are given to the conduit by this treatment as are givento the cable. For the purpose of generic definition I have adopted theterm covering for electrical conductors to designate both the conduit asa separate article of o manufacture, and the outer sheath which receivesthe impregnating and coating treatment as a component of an electricalcable I or single insulated conductor which may be treated by thismethod. 4 It will be noted that in the treatment of bothdescribed'embodiments of such coverings, according to this invention,the usual coating or impregnation by 'a sphaltum is omitted, and thewater-proofing effect is g fully and adequately obtained by thesubstituted wax treatment. Thus the wax performs the double function ofwater-proofing the article and mitigating the stickiness of theflame-proofing compound. And, in ap- 5 plication according to mydiscovery and in- 'vention, it performs these'functions without creatinga fire hazard.

What I claim and desire to secure by Letters Patent is: I so 1. Themethod of water-proofing and flame-proofing coverings for'electricalconductors which consists in fir t. impregnatingv such covering withwaxof a lower melting point than the after-mentioned flame proof- '35 ingcompound, and then enveloping said covering with a coat offlame-proofing com- Jpound which is liquefiable by heat and is appliedat a temperature higher than the melting point of the wax.

2. The method of water-proofing and flame-proofing coverings forelectrical conductors, and mitigating the stickiness of theflame-proofing substance, which consists in first applying to thecovering a waxy substance which is liquefiable at a temperature theatmospheric temperatures, but insufli cient to create a 'fire hazard.

i. A covering for electrical conductors having a water-proofing contentof wax on and adjacent to its outer surface, and an enveloping coatingof flame-proofing material interpenetrated to a certain extent by suchwax.

5. A covering for electrical conductors constructed of interconnectedfibrous strands having material which in itself is more or less stickyat ordinary temperatures, and having a content of wax within itsstructure inside of said coating and penetrating the latter to the outer'surface in suflicient measure to render such surface substantiallynon-sticky.

6. A covering for electrical conductors of textile construction,combined with a wax impregnation and a flame-proofing coat ng of stearinpitch, a portion of the wax being interspersed through said coating tothe outer surface thereof in sufficient measure to render such surfacesubstantially non-sticky, but insufiicient to create a fire hazard.

In testimony whereof I have aflixed my signature.

\ JOSEPH A. KENNEDY.

lower than that to which the flame-proofing substance is brought whenapplied to the covering, and also has the'property of penetrat' ing theflame-proofing substance when both are in the liquid condition; and thenapplying' to the article thus treated a coating of flame-proofingcomposition at a temperature high enough to'melt the waxy substance.

penetrate through such stearin pitch coating in suflicient quantity tomitigate the sures face stickiness ofjthe latter, when cooled to 3. Themethod of water-proofing and i

